1. Technical Field
The present invention relates to a light-emitting device, a display device, and an electronic apparatus.
2. Related Art
An organic electroluminescence (EL) device is a light-emitting device, which has a configuration in which at least one organic light-emitting layer is disposed between an anode and a cathode. In such a light-emitting device, an electric field is applied between the cathode and the anode with the result that electrons are injected from the cathode to the light-emitting layer and that holes are injected from the anode to the light-emitting layer. Then, the electrons recombine with the holes in the light-emitting layer with the result that the excitons are generated. The excitons return to a ground state and thereby generate energy, and the energy is released in the form of light.
Examples of such a light-emitting device include one of a type in which at least two light-emitting units (light-emitting sections) having light-emitting layers are provided between a cathode and an anode and in which a carrier generation layer is provided as an intermediate layer between the light-emitting units, the carrier generation layer having a function of generating carriers (electrons and holes) (for example, see JP-A-2003-272860).
In such a light-emitting device, an electric field is applied between the anode and the cathode with the result that electrons and holes are generated from the carrier generation layer. Therefore, the electrons and holes are supplied to the light-emitting layers included in the light-emitting units that are provided so as to be positioned adjacent to the carrier generation layer. Accordingly, in addition to the holes and electrons that are respectively supplied from the anode and the cathode, the electrons and holes that are supplied from the carrier generation layer are also used to emit light from the light-emitting layer included in each of the light-emitting units. Consequently, in cases where a constant current is applied to such a light-emitting device, the light-emitting device is capable of emitting light with high luminance and has excellent light emission efficiency, as compared with a light-emitting device having one light-emitting layer. Furthermore, also in cases where such a light-emitting device is used at a low current, light is capable of being emitted with relatively high luminance, and therefore the performance of the light-emitting device is less degraded, and relatively long emission lifetime is provided.
However, in such a light-emitting device, a metal oxide such as V2O5 or indium tin oxide (ITO) is used as a material of the carrier generation layer (intermediate layer). Therefore, a driving voltage of the light-emitting device is increased. In addition, the metal oxide contained in the carrier generation layer reacts with organic materials contained in the light-emitting units with the result that a problem is caused in that the lifetime of the light-emitting device is decreased.